Electromagnetic control device



May 12, 1959 KELTO 2,886,669

ELECTROMAGNETIC CONTROL DEVICE Filed Dec. 24, 1956 v 4 Sheets-Sheet 1 IN VEN TOR JV/Wan;

A-r'ToRuaY y 1959 R. E. KELTO 2,886,669

ELECTROMAGNETIC CONTROL DEVICE Filed Dec. 24, 1956 4 Sheets-Sheet 3 4 17 45 Bags 45 "4 INVENTOR I Y a I I I 7 \al 49: y 4: f ol vlz fllCeJzo yam- AT-roahev R. E- KELTO ELECTROMAGNETIC CONTROL DEVICE May 12, 1959 4 Sheets-Sheet 4 Filed Dec. 24, 1956 E INVENTOR Budd of: EKeJto ATTORNEY United States Patent ELECTROMAGNETIC CONTROL DEVICE Rudolph E. Kelto, Milwaukee, Wis., assignor to Cutler- Hammer, Inc., Milwaukee, Wis., a corporation of Delaware Application December 24, 1956, Serial No. 630,335

4 Claims. (Cl. 200-104) This invention relates generally to electric control devices and more particularly to electromagnetically actuated switches which are suitable for use as contactors or relays.

It is an object of this invention to provide an electric control device with high performance characteristics which is more economical to manufacture than prior art devices.

Another object is to provide a switch of this type which operates in all positions quietly without chattering of the electromagnet.

These objects are obtained by mounting the magnet frame so that it rocks to make flush contact with pole faces of the armature, placing the greatest mass in the movable armature, loosely guiding such armature in its path, and providing return springs for the movable armature. When energized these features cooperate to tightly lock the armature and frame and prevent chattering and permit the device to be used in all positions.

The coil of the electromagnet may be loosely mounted between the magnet frame and the movable armature with the return springs placed to react between it and the movable armature. This also helps in establishing proper flush contact between magnet frame and movable armature and permits easy assembly and disassembly.

A switch having these characteristics is hereinafter described and shown in detail in the drawings, in which:

Fig. 1 is a view in front elevation of a switch embodying the invention with parts broken away and shown in section;

Fig. 2 is a sectional view taken on line 2-2 of Fig. 1, showing the electromagnet de-energized and the switch open;

Fig. 3 is a sectional view also taken on line 2-2 of Fig. 1 and showing the electromagnet energized and the switch closed;

Fig. 4 is a sectional View taken on line 44 of Fig. 1;

Fig. 5 is a perspective view of the movable armature and adjustable linkage;

Fig. 6 is a bottom view of such armature;

Fig. 7 is a fragmentary sectional view taken on line 7--7 of Fig. 2; and

Fig. 8 is a fragmentary sectional view taken on line 88 of Fig. 7.

. The switch shown in the drawings is designed for handling up to 20 amperes at 250 volts A.C. with three poles. The rating of the switch may be varied and it may be furnished in 2, 3 or 4 pole versions within the scope of this invention. The induction coil is generally designed for 24 volts at 60 cycles AC. The elements of the switch are contained within or mounted on an insulating housing 10, the novel characteristics of which will be described in detail in connection with the description of the switch elements. This housing has many characteristics well known to those skilled in this art which are designed to prevent voltage leakage and flash-over and provide for proper heat dissipation and the like. These will not be described in detail except where not apparent. When the switch is fully assembled, a mounting plate 12 is secured to the rear of the housing to hold the parts in place and provide means for mounting the switch to a panel in the position shown in Fig. 1.

The contact assemblies of each pole are mounted on the outside of a dividing wall 13 between sides 14 and are separated by partitions 16. Each such contact assembly includes a pair of fixed contacts 18 and 20 and a bridging contactor 22. All contacts include silver composition contacting portions mounted in a standard manner. The fixed contacts 20 may have additional offset extensions with terminal screws. All of the fixed contacts are located by interfitting tongue and grooves indicated at 24 and are rigidly secured by screws 26 threadedly engaged with inserts molded into the housing at appropriate places. These screws may also act as terminal screws. The bridging contactor 22 is part of a movable contactor assembly which consists of a fiat insulating plunger 28, the bridging contactor 22, a compression spring 30 and a locking cup 32. The plunger is narrowed to form shoulders 34 at the base of a tongue. The contactor 22, being provided with a rectangular shaped opening, loosely rides on such tongue and is resiliently urged against such shoulders by the compression spring. The spring and contactor are removably held on such tongue by the locking cup 32. The locking cup has a noncircular opening 36 adapted in one position to slide on to the tongue. However, when the cup is rotated the sides of such opening will enter indentations 38 in the tongue and hold the cup on the tongue with the spring under compression. To make sure that the cup will not rotate from the locked position during normal operation, the cup may have depressions 40 into which the edge of the indentations 38 seat. However, the cup may be unlocked by forcibly rotating it until the non-circular opening aligns with the tongue. The insulating plungers 28 are slidably mounted in rectangular openings 42 on the dividing wall 13 and their inner ends project to the rear side of such wall and have small openings 44 by which they are connected to the electromagnetic operating means as hereinafter described. An enclosed pocket 45 for each of the contact assemblies is completed and closed by a cover 46 having sides 48 which snugly fit between adjacent ones of the sides 14 and partitions 16; the ends of the sides 48 resting on the fixed contacts 18 and 20 to hold the contacts in place when screws 26 are loosened. The sides 48 have slots 49 which accommodate the reduced sections of the partitions 16 between the grooves 24. This creates a cornered or tortuous path between adjacent pockets. These pockets confine any ionization due to arcing and thus increase the resistance to short circuiting.

The electromagnetic means for operating the contact assemblies is on the inner side of the dividing wall 13 between the sides 14; there being protecting walls 50 extending between the sides 1 to form a recess in which part of such means is located. The electromagnetic means consists of a movable armature 52, an induction coil 54, and a magnet frame 56.

The movable armature 52 is loosely slidably mounted between guides 58 extending from the protecting walls 50, the upper one of which is notched at 60 to facilitate assembly. In comparison with the magnet frame 56, the movable armature has much greater mass. It has three spaced legs 62 which are as long as the coil 54 with the center leg operating within the central opening of the coil. The outer (toward the right as viewed in Figs. 2 and 3) stroke of the movable armature is limited by engaging projections 64 on the dividing wall 13. Its inner or contact closing stroke is limited by engaging the magnet frame 56. As is standard practice shading coils 65 may be employed on the armature 52.

- The induction coil 54 is wound bobbin style on a molded insulating frame 66 having an open core loosely receiving the center one of legs 62, an inner end plate 68 and an outer end plate 69 having spring centering projections 76. The coil is loosely mounted with its outer end plate 69 within and laterally guided by the protecting walls 59 and guides 58 at the ends thereof. Projections 72 formed between the protective walls 50 and guides 58 have ends which engage the end plate 69 to limit'its outer movement. The coil is held on the seat thus formed by magnet frame 56 engaging the end plate 68 and can move slightly in all directions to adjust for variable manufacturing dimensions and to prevent any frictional locking between the movable armature and such coil. The coil has leads 73 which are secured to conveniently placed terminals. The windings of the coil are not enclosed by any part of the housing and free circulation of air there- .about is obtained to dissipate the heat of the coil.

The magnet frame 56 has its ends positioned in recesses 74 formed in the sides 14 and seats against convexly curved bottoms 76(see Fig. 3) when the electromagnet is energized. This permits the magnet frame to rock and establish a fiat surface to surface engagement with ends of the armature legs 62 to eliminate chattering and other objectionable noise and the necessity of maintaining costly close tolerances in manufacture.

It has been found preferable to resiliently return the armature 52 to switch open position and thus permit the switch to be used. in any position. This is accomplished by coiled compression springs 78 seated on the spring centering projections 70 and on brackets 80 at tached to the armature, such brackets also having spring centering projection 82. The springs 78 are within the protecting walls 59 and at times may be guided thereby. Springs 78 are so selected that upon de-energization of coil 54 they will overcome inertia and friction of the armature and contact assemblies and move the latter to open circuit position.

The contact assemblies are each connected to the movable annature 52 by an adjustable linkage which allows each contact assembly to be independently adjusted. Each contact assembly has its spring 30 which will be com pressed after the bridging contactor 22 engages thefixed contacts 18 and 26 as the movable armature 52 moves into face contact with the magnet frame 56. As the silver composition contacting portions wear, goodcontact will still be obtained by the action of the springs 34 allowing the necessary overtravel to provide such wear allowance (say .053 to .059 inch). Since it is good practice to have contact pressures in the neighborhood of 7% oz. to 8 A 02., it requires considerable force from the electromagnetic operating means to compress such springs prior to the closing of the magnetic gap. If the wear allowance range is maintained with close tolerance the electromagnetic force is lessened and smaller coil capacity is required. To provide for .such small wear allowance range tolerance eachcontact assembly is prefer: ably individually adjustable. To accomplish this a side plate 34 having a deformable finger 86 for each contact assembly is secured to the movable armature 52. .These fingers are offset from the end of armature 52 and slidably fit in the openings 44 of the plungers 28. When such armature is held against movement each plunger can be separately moved to bend its finger to the position affording the desired wear allowance.

To set the contacts for a wear allowance within the range from .(l53.059 inch, a gage having a thickness of .053 inch is placed between the movable armature 52 and the magnet frame 56. Coil 54 is energized to lock the armature. The deformable fingers 86, having been roughly set so that there is no contact between bridging contactor-s and fixed contacts 29 under these conditions, are each separately bent by pushing each bridging contactor into contact with the stationary contacts. The point at. which contact is made can be accurately determined by a test lamp connected across the fixed contacts. 'fter this adjusting operation is completed the .053 inch gage is removed and a .059 inch gage is inserted in its place and the coil 54 is again energized. If the test lamp fails to light then the contact assembly so tested is properly adjusted and falls within the desired range. However, if the lamp lights, such contact assembly is too tight and the fingers 86 should be bent by slightly pulling the plunger 23 of such assembly. A recheck of this assembly with the .053 gage must then be made.

The assembly of the switch may be accomplished by placing the plungers 28 in the openings 42 of the dividing Wall with the openings 44 lying beneath the notches 60. The armature 52 is then slid in between the walls 5'6 while raised in the notches 69 until the fingers 86 are aligned with the openings 44. The armature may then be lowered to normal position and moved into engagement with the projections 64. The bridging contac- .tors 22, springs 30 and cups 32 can now be assembled. Thereafter the return springs 78, coil 54, magnet frame 56 and mounting plate 12 are assembled in that order. No fastenings are required except for the mounting plate 12 which holds the parts in operating position. When the coil 54 is energized the parts move from the positions shown in Fig. 2 to the positions shown in Fig. 3. During such movement the contacts are engaged and the springs 30 and 7S compressed. The relatively light magnet frame 56 freely'rocks on the convex surfaces 76 and makes flush contact with the armature 52. The positioning of the coil 54 by reason of the magnetic field is substantiallyneutralized and only the light force .of springs 73 urges the coil toward the magnet frame. Hence, all parts are easily aligned and maximum holding force developed whil; enjoying quiet operation.

The momentum imparted to the heavy armature 52 carries it through the critical oscillatory point near its engagement with the magnet frame.

I claim:

1. An electric control device comprising an insulating support having guides integral therewith, a station- 1 ary contact on said support, a movable contact cooperable with said stationary contact, a movable armature linked to said movable contact and loosely guided by said guides, an electromagnetic coil loosely directly mounted on said support for slight movement in all directions, and a magnet frame loosely carried by said support, said support having abutting means engaging said end portions for providing rocking of said frame to provide flat engagement between said frame and movable armature upon energization of said coil.

2. An electric control device according to claim 1 in which said rocking means consists of convex surfaces onsaid support againstwhich said end portions bear when said coil is energized to establish fiat contact with said armature.

3. An electric control device according to claim 2 in which said movable armature has more mass than said magnet frame.

4. In an electromagnet, a support having convex curved portions, a coil held by said support, armature guides on said support, a movable armature loosely carried by said guides, and a loosely mounted magnet frame having end portions extending beyond said movable armature, said end portions contacting said convex curved portions to allow alignment between said armature and said frame to establish a fiat surface to surface engagement therebetween upon energization of said coil.

References Cited in the file of this patent UNITED STATES PATENTS 1,563,670 Spencer Dec. 1, 1925 2,036,295 Piffath Apr. 7, 1936 2,087,895 Bierenfeld July 27, 1937 2,378,162 Stapleton June 12, 1945 2,513,695 Van Valkenburg July 4, 1950 2,692,314 Lawrence Oct. 19, 1954 2,721,963 Knight Oct. 25, 1955 

